Recently, as a result of the popularization of low-priced CCD camera and CMOS camera and the enhancement of the performance of a personal computer, the execution of real-time image processing has been facilitated. As a result, fields, to which real-time image processing has applied, are fast widened. For example, a processing object of the real-time image processing has widened from an artificial thing having a simple shape to a human figure having a complex shape. In the future, real-time image processing is expected to be applied to wide fields such as game play, surveillance of a figure, authentication of a person, equipment operation interface, acceptance, service and robotics.
A fight game by two characters produced by CG applying real-time image processing technique is popular. In a conventional type of game, operations such as a punch are input by inputting a command to a dedicated operator console. Lately, a fight game in which a player acts such as by actually punching and imaginarily fights in a computer attracts attention. For example, a fight game in which actions are input such as when a player wears an acceleration sensor and acts is known (for example, refer to JP-A No. 285249/1994 and JP-A No. 49436/2004).
However, in the fight game according to the prior art, a player is required to wear a special sensor on a hand and other portions of the player. Besides, the fight game has a problem that only the acceleration of the hands and feet on which the sensor is mounted can be measured. Further, the fight game also has a problem that a cumulative error is caused when a position is computed based upon acceleration information measured by the acceleration sensor.
A game in which the operation of a player imaged by a camera is input to a computer and the player imaginarily fights in the computer is known (for example, refer to JP-A No. 53563/1999). In such a game, as the operation of the player is measured using not a sensor but a camera, information including the acceleration of the hands and feet can be simultaneously acquired real-time.
However, the conventional games have a problem that distance between a camera and a player cannot be measured. Further, these games have a problem that only a position on a two-dimensional plane perpendicular to the optical axis of a camera can be measured. In a fight game, for example, the information of a three-dimensional position of a player is important. Thus a need exists for the ability to measure a three-dimensional position of a tracking object imaged by a camera.